Tensile deformation of silver micro-wires of small thickness-to-grain-size ratios

► We identified a new regime of size effect of strength in polycrystalline samples. ► This occurs in micro-sized specimen when specimen size to grain size ratio is low. ► In this regime, Hall-Petch relation is not obeyed for the grain size. ► TEM examination reveals that dislocation density remains low in this regime.